No one wants to stay in a bad mood, so you can try doing creative exercises or understand the science to turn it around. But one of the easiest ways to get out of your funk is to help out someone else, says Caroline Adams Miller, a Maryland-based author and psychologist specializing in Applied Positive Psychology.

Taking the time to do something nice for another person helps change your mindset, she explains. It can be something as small as thanking a colleague for their help on a project, or going out of your way to help someone else. Miller says:

Altruistic behavior gives you the 'helper's high' and there are many ways to do something generous or kind in a few short minutes.

The full article at Fast Company has some other cool tips on changing a bad day, including Miller's advice to hold a pen in your teeth and nod vigorously—really!